[An evaluation of the functional lip posture].

Abstract

The purpose of this study was to evaluate the relationship of the functional lip posture to the anterior teeth and gingiva and at the same time establish an objective esthetic standard in the clinic. The functional lip posture referred here were the smiling lip line and the maximum opening lip line. From an esthetic and clinical point of view, the functional lip posture was described, classified and scored using the relationship of the border of the upper and lower lip to the labial surface of the anterior teeth and gingiva. A device for taking standardized oral photographs with a high degree of reproducibility was used. Tjan, et.al. studied the esthetic factors in a smile. Using their classification the result of this study were as follows: high smile, 32%; average smile, 42%; and low smile, 26%. The difference in the amount of maxillary and mandibular gingival exposure were also determined in this study. The measurement of the maxillary area was used in classifying the smile since the mandibular area showed interproximal gingiva only. In analyzing the maximum opening lip line, it was not possible to apply Tjan's classification since it referred only to the smile line. A scoring system (smile score) was devised, instead, to evaluate the functional lip posture. By this scoring system, the smiling lip line was classified using the maxillary teeth and gingiva only. The classification were as follows: high smile, score was over 4; average smile, from 3-4; and low smile, under 3. Note that the maxilla was used as reference in analyzing the smiling lip line and the mandible for the maximum opening lip line.